For some people 100$ are like millions and for some millions are nothing its not about how much HW wallets are about holding, I bought a new person in crypto he wants me to setup a HW wallet and then he question how can i trust this secret key when someone else is telling it I want to create it manually and there is no option to do so. I said for now you have to trust them, its new yet soon you can do it manually too.
If there is way to do so please share a link or wallets providing this type of facilities.
The gist of your question here is that you choose not to trust anyone else. Then, you probably shouldn't trust your own computer either. Most of your OS and firmware are not open source and are known to have backdoors previously. If you don't trust independent audits or the source code of the hardware wallet, then I would urge you to just do it by hand, because by your logic, nothing is safe.
Your hardware wallet should be new and direct from the manufacturer with unopened seal. If you don't want to trust the manufacturer, you can use a pen and pencil, create your private keys, make your own transactions and broadcast it. Hardware wallet manufacturers have a reputation to uphold, the fact that any possible backdoors would destroy their business is a sufficient deterrence. If you don't trust their entropy, use your own. Otherwise, this topic has been discussed to death and the conclusion is almost always, if you don't trust them then don't use them. There is no way to mitigate your irrational fear if you can't feasibly construct your own hardware wallet from scratch.